Selective laser sintered fused deposition printing

ABSTRACT

A method of additive manufacturing of an object includes directing laser energy from a laser to a region for material deposition, extruding material using an extruder at the region of material deposition, sensing temperature within the region of the material deposition, and electronically controlling the laser energy using the temperature so as to sufficiently heat the region for material deposition prior to extruding the material to increase strength of the object.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/354,992, filed on Jun. 27, 2016, and entitled “Selective LaserSintered Fused Deposition Printing”, hereby incorporated by reference inits entirety.

FIELD OF THE INVENTION

The present invention relates generally to 3D printing of single ormulti-materials using combined selective laser sintering and fuseddeposition of materials.

BACKGROUND OF THE INVENTION

Selective Laser Sintered (SLS) is typically done using a powder bed anda laser at a set power and spot size which sinters plastic or metalpowder. Fused Deposition Printing (FDP) is also known as Fused FilamentFabrication (FFF). FFF has a specific trademark of Fused DepositionModeling (FDM) and this is common language in the 3D printing world. FFFuses a filament, and while FDP is identical in many ways to FFF, it maynot require a filament as the material feed. FDP can use filament,pellets or powder. These three use heated nozzles that meltsthermoplastic material and forces it through a small orifice. The firstlayer of printing is important and if good adhesion is not achieved, theprint will curl and the next layer will not adhere. To accommodate this,a heated bed or a glue base is used to capture the first layer. A heatedbed helps the second layer adhere to the first layer and this continuesto many layers. If the structure is too large, the top layers are muchhotter than the cooled layers below and this will cause the object todelaminate.

SLS uses a powder bed and the laser has a given spot size that willprovide localized heat that sinters the spot size region. Scanning orpatterning is done in two dimensions. Once the pattern is complete athin layer of thermoplastic has been fused or sintered to make a singlepiece. The single layer or pattern is lowered and a second layer ofpowder covers the first layer. The laser patterns again, fusing thelocalized spots deep enough to fuse to the first layer. This is done asmany times as needed to build the object. SLS objects have good strengthproperties in all dimensions and does not suffer the same delaminationissues due to the printed layers.

What is needed are new methods, systems, and apparatus that provide forimproving over SLS and FDP processes.

SUMMARY OF THE INVENTION

According to another aspect, a method of additive manufacturing of anobject includes directing laser energy from a laser to a region formaterial deposition, extruding material using an extruder at the regionof material deposition, sensing temperature within the region of thematerial deposition, and electronically controlling the laser energyusing the temperature so as to sufficiently heat the region for materialdeposition prior to extruding the material to increase strength of theobject.

According to another aspect, a system for additive manufacturingincludes an extruder for extruding a material onto a surface, a laserfor directing laser energy onto the surface, a heat detector for sensingtemperature at the surface, and a control system operatively connectedto the extruder, the heat detector, and the laser. The control system isconfigured to control the directing of the laser energy onto the surfacebased on the temperature at the surface sensed using the heat detectorto heat a region of the surface prior to extruding the material onto thesurface.

According to another aspect, a method of additive manufacturing of anobject is provided. The method includes directing laser or LED energy ina region of material deposition as an ultraviolet (UV) curing lightsource, and controlling the laser power in a closed loop feedback fromtemperature sensing in the deposition region.

According to another aspect, a method of combining Selective LaserSintering and Fused Deposition Printing in a single process includesextruding material using a Fused Deposition Printing approach, directinglaser energy in a region of material deposition, and electronicallycontrolling the laser power in a closed loop feedback from temperaturesensing in the deposition region.

According to another aspect, a method of using a laser to prepare asurface for Fused Deposition Printing includes directing laser energyfrom a laser to a region of material deposition, with the laser energybeing either pulsed or continuous wave, texturing the surface using thelaser energy, and extruding material on the surface of the textured areausing Fused Deposition Printing or other Direct Print methods.

According to another aspect, a method of using a laser to remove andreplace defective material as a repair process includes directing laserenergy in a region of material for removal, directing laser energy in aregion of material deposition (the laser energy being pulsed orcontinuous wave), and extruding material onto the surface to repair.

According to another aspect, a method includes using a laser or a millto smooth a defective area and then using a laser and temperaturefeedback to restart or continue a printing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the system. The block diagram shows a printhead, a laser source, a detection source, an XYZ motion and a controllerthat integrates these for synchronous motion and control.

FIG. 2 is a diagram of the printer with the laser and thermal detectorpointing at a common point on an XYZ stage.

FIG. 3 is a diagram of a system.

FIG. 4 is a diagram of a system including a ring of fibers whichincludes both laser emitters and light detection for heat sensing.

FIG. 5 is a diagram showing a ring of fibers which may be positionedaround a pen tip.

FIG. 6 is another diagram showing a ring of fibers around a pen tip of anozzle.

FIG. 7 is a diagram of two layers being fused together in XY plane.

FIG. 8 is a diagram of multiple layers prior to being fused together inthe YZ plane.

FIG. 9 is a diagram of multiple layers after being fused together in theYZ plane.

FIG. 10 is a diagram of a surface being pitted.

FIG. 11 is a diagram of the surface being printed on after the pittingto promote better adhesion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Combining SLS and FDP allows solid lines or patterns to be printed usingFDP in 2 dimensions. Any place a line is printed and a second line isjoined to the first line in 2 dimensions there is still a weak pointthat can delaminate. Joining these two lines using a laser to melt orweld the seam provides strength. This can be done in real time using afocused temperature feedback reader such as a bolometer and a laser. Thetemperature can be accurately controlled and this provides perfectmelded seams. The second layered pattern which is similar to fusing twolines that are in an XY plane touching each other, but this is two linesin the XZ or YZ plane and still touching each other. The laser isutilized and will lead the print therefore making a thin liquid levelfor the new material to be printed in. This will unite the layers as asingle material and reduce or eliminate the delamination issue.

This approach will eliminate the need to print on heated beds. The laserwill heat a plastic or metal surface and this will promote adhesion. Forplastic surfaces, the laser will provide a small melt zone and theprinted layer will then be melt to melt. For metal layers the mismatchin material types will challenge adhesion. To accommodate this, thelaser may be put in pulsed mode and tiny micro-pits will be made in thesame pattern as the pattern to be printed. The print will begin and thelaser will heat the metal thus allowing the melted thermoplastic to poolin the micro-pits. When this cools, a small amount of shrinkage willoccur and pull the plastic tight into the pits and adhesion will occur.It is possible with this approach to print on any existing object or tobegin a print and stop. Take out the printed object and then put it backfor immediate continued printing.

The present invention recognizes the need for enhancing 3D printedobjects. The combination of SLS and FDP on a single platform andcontrolled by one controller for synchronous and consistent results isobtained by strategically placing fibers for the laser and the detectionnear the pen tip. In some cases the detector cannot be fiber fed and mayneed to be in proximity to the pen tip. Small micro-lenses may beprinted on the fiber ends to provide focusing of the laser. The numberof lasers can range from one (1) to a continuous ring of lasers or tens(10s) to hundreds (100s) of fibers. The optimal number will depend onthe specific application, but eight (8) allows for a symmetrical numberof laser spots that would encircle the pen tip. This allows for thematerial to be heated from several angles.

The laser being coupled into the fiber may be a range of lasers, but adiode laser is efficient, compact, rugged and cost effective. The diodemay be coupled into the laser at a distance set by the length of thefiber optic cables. These are very low loss, so meters are essentiallylossless. Depending on the power requirement this may be one (1) laserper fiber or one (1) laser and a galvo that moves the laser to a chosenfiber.

The heat detector may be a non-contact detector and a common detectorfor this is a bolometer although other types of heat detectors may beused. A bolometer may provide a good resolution that matches the size ofthe prints and the laser spots coming from the fiber optic cable. Thebolometer provides fast thermal readings. These readings are put in aclosed loop feedback system that controls the laser power output. Thelaser power output can range from milliwatts to tens (10s) or hundreds(100s) of watts of power and this is near instantaneous. This changesthe temperature on the spot in near instantons times matching thefeedback for controlling the temperature of the spot.

The spot size may range from single digit microns to millimeters. Insome cases it may be necessary to make the spot size tens (10s) or evenhundreds (100s) of millimeters. The spot size may match or nearly matchthe size of the print from the pen tip. The laser may heat a localizedarea instantaneously to allow the newly printed material that isextruded from the pen tip to match temperatures. The extruded materialfrom the pen tip may range from room temperature to hundreds (100s) ofdegrees Celsius. The temperature requirement depends on the materialbeing extruded through the pen tip. Any number of different materialsmay be used. The material being extruded may reach a melt temperatureand reach a liquid state or near liquid state. The material exits thehot pen tip and quickly cools, since the volume of the liquid is smallas compared to the surface area. This is a localized process and thelaser is also a localized process. The localized process will traversein a specified direction at a specified speed. The direction can be anydirection in an XYZ coordinate system. The speed can vary from veryslow, such as less than one (1) mm per second to more than one (1) meterper second. Typical speeds are in the range of tens (10s) to hundreds(100s) of millimeters per second. The laser may heat at linear speedsthat match the print speeds. This creates a match of localizedtemperature of a substrate or of one layer to the next layer andtherefore fusing more completely the layers.

FIG. 1 illustrates one example of a system 10. A control system 12 isshown which may be used to control an XYZ stage or other stage. Thecontrol system 12 is operatively connected to a microcontroller 18 orother intelligent control and a thermoplastic extruder 22. Thethermoplastic extruder 22 provides for extruding or printing moltenplastic onto a surface 24. The microcontroller 18 receives temperatureinformation from a heat detector such as a thermal imaging detector orbolometer 16. The microcontroller then controls a laser 20 to emit laserenergy to the surface 24. The laser may use a laser diode or other typeof laser. The laser energy may be pulsed or may be continuous.

In operation, the heat detector such as bolometer 16 may measureinfrared, or heat radiation including a spot temperature on the surface24. The temperature data may then be communicated to the microcontroller18. The microcontroller 18 may then control the laser 20 based on thetemperature data so as to stop heating the surface 24 or to continueheating the surface 24 with laser energy. This heating is performed on aregion of the surface prior to extruding molten plastic by thethermoplastic extruder 22 in order to prepare the surface.

FIG. 2 illustrates one example of portions of the thermoplastic extruder22 of a 3D printer. A nozzle 30 is shown with a tip 32. Both a laser 16and a thermal detector 20 point at a common point on an XYZ stage 33.

FIG. 3 illustrates another diagram of a system. As shown in FIG. 3, acontrol 12 is operatively connected to a microcontroller 18. Themicrocontroller 18 may provide a current signal to control a laser 20.The laser 20 emits laser energy to a surface 24 to heat the surface. Aheat detector such as a thermal imaging detector or bolometer 16 may beused to determine surface temperature of the surface 24.

FIG. 4 illustrates another example where there are a plurality of heatdetectors or thermal imaging detectors or bolometers 16 and a pluralitylasers 20 which may be configured in a ring around the thermoplasticextruder 22.

FIG. 5 is another view where there is a ring of bolometers and lasersconfigured in a ring around a nozzle 30 having a tip 32. As shown inFIG. 5, fibers 60 for the laser and fibers 62 for the heat detector(s)may be used.

FIG. 6 is another view of a ring of fibers with detectors 60 such asbolometers and fibers with lasers 62 configured in a ring around anozzle 30.

FIG. 7 illustrates interaction between a laser beam 52 and a surface 24.The laser beam 52 travels in a direction 68 and heats the surface 24 toform a melt pool 72 along a seam 70 which allows for a welded seam 74 tobe formed. Thus, The two layers are then fused together in the XY plane.

In addition to its use in welding seams, the laser beam 52 providesother uses. For example, a control system may determine that a region ofmaterial deposition has a defective area. Thus, instead of continuingwith the build process, the laser may return to the region which has thedefective area and the defective area may be reheated with the laser toprovide for smoothing of the defective area. Alternatively, thedefective area may be milled or otherwise processed. Thus, depositedmaterial may be removed.

FIG. 8 illustrates a surface 24 before welding where seams 70 arepresent and in the YZ plane. FIG. 9 illustrates the surface 24 afterwelding where the seams have been welded to form welded seams 74 and inthe YZ plane. The method described allows for the strength of the objectbeing 3D printed to be increased by reducing susceptibility ofdelamination of layers of the object due to the improved adhesion.

FIG. 10 illustrates a surface 24 where a laser beam 52 has made aplurality of micro pits 50 in the surface 24 to produce a pittedsurface.

FIG. 11 illustrates the surface 24 with micro pints 50 where material 76from a nozzle 30 is dispensed or written or otherwise extruded on thesurface 24 and fills in micro pits 50 as it is extruded. This pitting ofthe surface 24 with the laser followed by the printing assists inpromoting adhesion between the layer being printed and the previouslayers. It should be appreciated that the laser may be used to texturethe surface or otherwise prepare the surface in any number of ways toassist in promoting adhesion.

Therefore, various methods, systems, and apparatus have been shown anddescribed for additive manufacturing. Although specific embodiments havebeen provided herein, the present invention contemplates numerousadditions, variations, options, and alternatives.

What is claimed is:
 1. A method of additive manufacturing of an objectcomprising: providing a system for additive manufacturing comprising: anextruder for extruding a material onto a surface, a laser for directinglaser energy onto the surface, a heat detector for sensing temperatureat the surface, a control system operatively connected to the extruder,the heat detector, and the laser, wherein the control system isconfigured to build the object comprising a plurality of layers of thematerial and to control the directing of the laser energy onto thesurface in a closed feedback loop based on the temperature at thesurface sensed using the heat detector to heat a region of the surfaceformed from a prior layer of the material prior to extruding thematerial onto the surface to form a current layer; directing laserenergy from the laser to a region for material deposition; extrudingmaterial using the extruder at the region of material deposition;sensing temperature within the region of the material deposition usingthe heat detector; and electronically controlling the laser energy in aclosed feedback loop using the temperature sensed within the region formaterial deposition so as to sufficiently heat the region for materialdeposition with the laser energy prior to extruding the material;wherein the region for material deposition is a part of a prior layer ofthe material deposited using the extruder.
 2. The method of claim 1wherein the laser comprises a laser diode.
 3. The method of claim 1wherein the laser energy is pulsed laser energy.
 4. The method of claim1 wherein the laser energy is continuous wave laser energy.
 5. Themethod of claim 1 wherein the laser energy textures the region formaterial deposition.
 6. The method of claim 1 further comprisingremoving deposited material at the region for material deposition usingthe laser energy from the laser.
 7. The method of claim 1 wherein theheat detector is a bolometer.
 8. The method of claim 1 wherein the heatdetector is a thermal imaging detector.
 9. The method of claim 1 whereinthe laser energy is conveyed from the laser through a fiber deliverysystem.
 10. The method of claim 1 wherein a plurality of fibers are usedin sensing the temperature and directing the laser energy.
 11. Themethod of claim 10 wherein the plurality of fibers are arranged in aring configuration around a pen tip of the extruder.
 12. The method ofclaim 11 wherein the laser energy textures a surface of the region ofmaterial deposition in order to prepare the surface.
 13. The method ofclaim 1 further comprising identifying with the control system theregion of material deposition as a defective area.
 14. The method ofclaim 13 wherein the directing the laser energy from the laser to theregion for material deposition provides for smoothing the defectivearea.
 15. The method of claim 14 further comprising milling thedefective area.
 16. A system for additive manufacturing, comprising: anextruder for extruding a material onto a surface; a laser for directinglaser energy onto the surface; a heat detector for sensing temperatureat the surface; a control system operatively connected to the extruder,the heat detector, and the laser; wherein the control system isconfigured to build an object comprising a plurality of layers of thematerial and to control the directing of the laser energy onto thesurface in a closed feedback loop based on the temperature at thesurface sensed using the heat detector to heat a region of the surfaceformed from a prior layer of the material prior to extruding thematerial onto the surface to form a current layer.
 17. A method ofadditive manufacturing of an object comprising: directing laser energyfrom a laser to a region for material deposition; extruding materialusing an extruder at the region of material deposition; sensingtemperature within the region of the material deposition, wherein aplurality of fibers are used in sensing the temperature and directingthe laser energy, wherein the plurality of fibers are arranged in a ringconfiguration around a pen tip of the extruder; and electronicallycontrolling the laser energy in a closed feedback loop using the sensedtemperature in the region for material deposition to sufficiently heatthe region for material deposition prior to extruding the material. 18.A method of additive manufacturing of an object comprising: directinglaser energy from a laser to a region for material deposition; extrudingmaterial using an extruder at the region of material deposition; sensingtemperature within the region of the material deposition; andelectronically controlling the laser energy in a closed feedback loopusing the temperature sensed within in the region for materialdeposition so as to sufficiently heat the region for material depositionprior to extruding the material; wherein the region for materialdeposition is a part of a prior layer of the material deposited usingthe extruder; wherein the laser energy textures the region for materialdeposition.